1. Field of the Invention
The invention relates to a process for the reactivation of a catalyst, and more particularly, to a catalyst which is used for the removal of NO.sub.x from exhaust gases such as smoke. The invention also relates to an apparatus for the execution of the process taught by the invention.
2. Description of the Prior Art
Catalysts, which are used for the removal of NO.sub.x from exhaust gases, especially exhaust gases such as smoke containing dusts, lose their activity during use.
It was found that the activity of catalysts for the removal of NO.sub.x depends on the presence of compounds of the transition elements in their lowest stable oxidation phase. During operation, the transition element compounds are converted to higher oxidation phases. This is the reason for the reduction of the activity of the catalyst.
Another reason for the reduction of the activity of the catalyst is that dust is deposited in the pores of the catalyst, so that the catalyst is plugged up.
Some examples of catalytic technology are found in U.S. Pat. No. 4,259,312, entitled "Process And Apparatus For Catalytically Reacting A Reducing Gas And Water Vapor"; U.S. Pat. No. 4,235,604, entitled "Method For Processing Coke Oven Gas"; and U.S. Pat. No. 4,049,777, entitled "Method Of Waste Gas Treatment", all of which are assigned to a corporation associated with the assignee of the instant application.
Further examples of catalytic technology are found in U.S. Pat. No. 4,448,895, entitled "Process For Preparation Of Catalyst For Cleaning Exhaust Gases And Catalysts Prepared For The Process", and U.S. Pat. No. 4,503,162, entitled "Catalyst Systems For The Conversion Of Gases".
Examples of reactivation of catalysts useful in nitrogen oxide removal are described in U.S. Pat. No. 4,044,102, entitled "Method For Treating Exhaust Gases", and U.S. Pat. No. 4,043,939, entitled "Reactivation Of Catalysts Useful For Nitrogen Oxide Removal." All of the above-cited patents are incorporated herein by reference.